1. Field of the Invention
The present invention relates to a microscope lens barrel including a collecting lens and a deflecting optical system which deflects observation light emitted from the collecting lens.
2. Description of the Related Art
In microscopic observation in general, it is regarded as ergonomically desirable that an observer looks into the microscope at a nearly horizontal depression angle. It is said that, when the observer looks down into an eyepiece angled in a horizontal direction or slightly above the horizontal direction, the observer experiences less physical tension and feels less tired after long hours of microscopic observation. Conventional microscopes arrange a microscope lens barrel housing the eyepiece at such an angle that the depression angle of the line of vision of the observer is substantially horizontal. Further, in many conventionally-proposed microscope designs, users can adjust the arrangement appropriately so as to make the depression angle suitable for his/her constitution and the like.
In a lens barrel optical system described in Japanese Patent Application Laid-Open No. H8-278448, light emitted from an objective lens enters a collecting lens which emits the light vertically upward. A prism receives the light from the collecting lens and emits the light downward. A rotatably-arranged mirror reflects and guides the light to a binocular lens barrel unit. In this lens barrel optical system, linked rotations of the mirror and the binocular lens barrel unit enable flexible adjustment of the depression angle of the line of vision (i.e., depression angle). In this lens barrel optical system, the light emitted from the collecting lens is guided to the binocular lens barrel unit via a relay lens.
In a binocular lens barrel described in Japanese Patent Application Laid-Open No. H8-43740, the light emitted from a collecting lens is guided to an eyepiece via rotatably-arranged mirror and prisms. In this binocular lens barrel, the linked rotations of the mirror, the prisms, and the eyepiece realize a flexible adjustment of the depression angle.
In a depression-angle-variable lens barrel described in Japanese Patent Application Laid-open No. 2000-98237, light emitted from an objective lens comes into a collecting lens via a rotatably-arranged mirror. Light emitted from the collecting lens is guided to a binocular lens barrel unit via prisms. In this depression-angle-variable lens barrel, linked rotations of the mirror, the collecting lens, the prisms, and the binocular lens barrel unit realize flexible adjustment of the depression angle.
On the other hand, an eyepoint of an observer looking into an eyepiece, in other words, the position of the exit pupil of the eyepiece should not be too high so that the observer does not need to take an uncomfortable position during microscopic observation (for example, in a stretched state). Microscope apparatuses of today, however, need to accommodate various intermediate lens barrels such as a projecting tube housing an epi-illumination system between a microscope body and a microscope lens barrel. Such necessity tends to raise the eyepoint in the microscope apparatus. Therefore, in the microscope lens barrel as a single unit, desirably the eyepoint is lowered as far as possible so that the eyepoint is approximately at the same level as an arranged position of the collecting lens.
In a lens barrel optical system described in Japanese Patent Application Laid-Open No. H.8-278448, light emitted vertically upward from the collecting lens is returned downward by the prism. Therefore, the binocular lens barrel unit can be arranged at a low position, and the eyepoint (i.e., eye level) at approximately the same level as the collecting lens.
In the lens barrel optical system described in Japanese Patent Application Laid-Open No. H8-278448, however, since the light emitted from the collecting lens is returned downward, the mirror which reflects the returned light and a mechanism which holds and rotates the mirror must be arranged below the collecting lens. Then, in order to prevent vertical interference between the portion arranged below the collecting lens and the microscope body, the intermediate lens barrels, or the like, the microscope lens barrel as a whole sometimes must be placed at a higher position than is generally arranged. In brief, even when the eyepoint can be made substantially equal to the level of the collecting lens in the microscope lens barrel, the eyepoint of the microscope as a whole in which the microscope lens barrel is mounted may not be sufficiently low. Further, in the lens barrel optical system described in Japanese Patent Application Laid-Open No. H8-278448, the light emitted from the collecting lens is guided to the binocular lens barrel unit via the relay lens. Therefore, the lens barrel optical system includes a large number of elements which makes the overall configuration of the lens barrel optical system bulkier and also pushes up the manufacturing cost.
Still further, in a binocular lens barrel described in Japanese Patent Application Laid-Open No. H8-43740 and the depression-angle-variable lens barrel described in Japanese Patent Application Laid-Open No. 2000-98237, the mirror which rotates to adjust the depression angle is arranged in front of or immediately next to the collecting lens. Therefore, many optical elements arranged in the lens barrel have to rotate in conjunction with the mirror. Such rotating mechanism as a whole becomes larger and heavier. Hence, the overall rotating mechanism must have a rigid configuration to increase its rigidity. Such requirements complicate the configuration of the lens barrel, and push up the manufacturing cost.
On the other hand, in the lens barrel described in Japanese Patent Application Laid-Open No. 2000-98237, the collecting lens is difficult to share between two separate light paths, namely, a light path for camera observation of an image of the specimen and a light path for visual observation via the eyepiece (in other words, a light path for eyepiece). In the lens barrel described in Japanese Patent Application Laid-Open No. H8-43740, it is possible to use the collecting lens for both the light path for camera observation and the light path for eyepiece by, for example, making the rotatably-arranged mirror a half mirror and arranging the light path for camera observation on the half mirror. In this arrangement, however, the rotation of the mirror can cause lateral displacement of the light path for camera observation.